During inkjet printing ink drops are ejected through print-head nozzles on to a media sheet, such as paper. The nozzles through which ink drops are ejected may become clogged with paper fibers or other debris during normal operation. The nozzles may also become clogged with dry ink during prolonged idle periods. Generally, print-head service stations are used for wiping the print-head and applying suction or blowing to the print-head to clear out any blocked nozzles.
Ink drop detectors may be used to determine nozzle health, such as whether a print-head actually requires cleaning, whether nozzles have failed, etc. A light-scattering drop detector is one type of drop detector that involves directing light, such as laser light, at ejected drops. The ejected drops scatter the light, and a light detector detects the scattered light and outputs an electrical signal indicative of the scattered light. The signal may be analyzed to determine various drop characteristics. One problem with existing light-scattering drop detectors is that they do not give information about more than one nozzle at substantially the same time.